The leukocyte count was evaluated in 479 laboring gravida women. Increasing leukocyte counts appeared to be linearly related to the duration of elapsed labor (y = 0.2174x + 10.31; p less than 0.001; 95% confidence interval of the slope = 0.1414 to 0.2934). Isolated mild elevations and mild increases of leukocyte count in labor may be managed expectantly. Elevations greater than 2 SD are unlikely to represent normal variation; a diligent search for unapparent infection is warranted.